Preparation of hydrodesulfurization catalyst



United States Patent 0 3,177,160 PREPARATION OF HYDRODESULFURIZATIUN CATALYST Armand J. de Rosset, Clarendon Hills, 11]., assignor to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware No Drawing. Original application Dec. 6, 1960, Ser. No. 73389. Divided and this application Jan. 25, 1962, Ser. No. 168,815

4 Claims. (Cl. 252465) The present application is a division of my copending application Serial Number 73,989, filed December 6, 1960.

The present invention relates to the manufacture of alumina, and is directed toward the preparation of an alumina carrier material through a novel method which permits the alumina to be derived solely from aluminum sulfate as the source of aluminum. When employed as the carrier material for catalytically active metallic compurifying agent, or as a catalyst in and of itself. Alumina is most often utilized, however, a the carrier material for a wide variety of catalytically active metallic components in the manufacture of hydrocarbon conversion and hydrodesulfurization catalysts. One of the first commercial methods employed for the production of alumina involved the recovery of aluminum oxide from naturally-occurring clays and earths. This method involved a long, arduous process, and produced comparatively low-grade alumina which was relatively expensive.

Many investigations have since been conducted in regard to a variety of processes for the purpose of producing a relatively inexpensive, high-purity alumina. For example, precipitation methods have been studied whereby a weak alkaline material, such as an aqueous solution of ammonium hydroxide, is added to an aqueous solution of an aluminum salt to form a precipitate of alumina. However, due to certain physical characteristics imparted to the resulting alumina, which inherently result from the use of ammonium hydroxide with some of the aluminum salts, the precipitate thus formed is difficult to convert to a form which is suitable for serving any of the functions previously described. Consequently, more expensive alkaline materials must be employed as precipitants, and the precipitation methods become diflicult to justify economically. Similarly, although the alkaline precipitant may be suitable, not all of the salts of aluminum are advantageously employed. For example, when aluminum sulfate, readily obtainable in abundant quantities at comparatively low cost, is employed as the source of aluminum, the gelatinous precipitate resulting from the utilization of ammonium hydroxide is notoriously difficult to process to its final form. Washing to remove the various contaminants is extremely tedious, and although washing by filtration is employed, relatively long periods of time are required to produce an acceptable filter cake ticles, and, of greater importance, the relatively poor surface are characteristics which do not produce an alumina attractive for utilization as a carrier material for catalytically active metallic components.

The object of the present invention is to produce alumina from a solution of aluminum sulfate, the final alumina being substantially free from contaminating sulfate ions, by a method which avoids expensive procedures, and which alumina affords unexpected benefits when employed as the carrier material in the manufacture of hydrocarbon hydrodesulfurization catalysts. The method of the present invention involves precipitating a uniform, insoluble basic aluminum sulfate, and the subsequent hydrolysis of the same with a chlorine-containing compound prior to obtaining the filter cake which, upon drying and/ or calcining, yields the finished alumina.

As hereinbefore stated, the method of the present invention produces an alumina which is advantageously employed as a carrier material in the manufacture of a variety of hydrocarbon conversion catalysts. In particular, the alumina of the present invention is readily adaptable for use in a composite containing metals selected from the group consisting of chromium, molybdenum, tungsten, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mixtures of two or more. As hereinafter indicated, the alumina of the present invention is especially adaptable to the manufacture of hydrodesulfurization catalysts comprising at least one metallic component selected from the group consisting of Group VI-A and the iron-group of the Periodic Table.

Therefore, a broad embodiment of the present invention provides a method of preparing a hydrodesulfurization catalyst which comprises initially precipitating basic aluminum sulfate from a solution of aluminum sulfate, hydrclyzing the precipitate, while maintaining the resulting slurry at a pH less than about 7.0, with a chlorinecontaining compound in an amount to result in a formula weight ratio of alumina-equivalent to chloride ion within the range of from about 3:1 to about 50:1, washing the resulting hydrolyzed precipitate until the washed precipitate contains less than about 2.0 percent by weight of sulfate, drying and calcining to produce alumina, combining at least one metallic component selected from the group of the metals from Groups VI-A and VIII of the Periodic Table with the calcined alumina and thereafter drying and calcining the resulting composite.

A more limited embodiment of the present invention PIOVldCS a method of preparing a hydrodesulfurization catalyst which comprises precipitating basic aluminum sulfate from a solution of aluminum sulfate, hydrolyzing the resulting precipitate with hydrochloric acid in an amount to result in a formula Weight ratio of alumina-equivalent to chloride ion within the range of from about 5:1 to about 15:1, maintaining the resulting slurry at a pH less than about 7.0, washing the resulting hydrolyzed precipitate until the washed precipitate contains less than about 2.0 percent by weight of sulfate, drying the washed precipitate and calcining the same at an elevated temperature, thereafter combining, with the calcined alumina, from about 6.0 percent to about 30.0 percent by weight of molybdenum and from about 1.0 percent to about 6.0 percent by Weight of nickel, calculated as the elements thereof. V

In the present specification and appended claims, the term alumina-equivalent is designated to mean that quantity of aluminum oxide (A1 0 which would result if all the aluminum existing as basic aluminum sulfate were converted thereto. The alumina-equivalent is employed as a convenient means of determining the quantity of the chlorine-containing compound employed in the is below a level of about 2.0 percent by weight.

hydrolysis of the basic aluminum sulfate precipitated from the aluminum sulfate solution.

An essential feature of the present'invention involves. the precipitation, from a solution of aluminum sulfate, of basic aluminum sulfate. Al't-hough'any suitable meth- I .During the commiugling of the-ammonium hydroxide with the aluminum sulfate, the pH of the resulting basic aluminum sulfate slurry is controlled at a level of about 6.0; that is, within the range of from about 5.5 to aboutv 6.5. This procedure produces a basic aluminum sulfate having an aluminum to sulfate ratio of about 1.35. Following aninitial filtration procedure, to remove the great- .er proportion of water, the filter cake is hydrolyzed by s'lurrying with a chlorine-containing compound, maintaining the pH at below about 7.0. p The hydrolysis of the basic aluminum sulfate is effected through the'utilization of a suitable chlorine-containing .compound, the latter being employed in an amount to result in a formula weight ratio of alumina-equivalent to chloride ion Within the range of about 3:1 to about 50: 1, and, preferably, within the intermediate range of 5:1 to about 15:1. Suitable chlorine-containing compounds include ammonium chloride, hydrochloric acid, .etc., and

are employed insuch a manner as to maintain the pH of the resulting slurry at a level less than about 7.0. The hydrolyzed basic aluminum sulfate slurry is refiltered and Washed, preferably with an ammoniacal solution, until the sulfate ion concentration of the resulting filter cake Upon drying, at a temperature of from about 100 C. to about 400 C., the alumina is in the form of talc-like powder having a particle size of about five to about ten microns.

The alumina is thereafter subjected to high-temperature calcin-ation, usuallyat a level of about 400 C. to-about I 800 C., and in the presence of a free-oxygen containing atmosphere, such as air. The calcined alumina is then formed into the desired size and/ or shape, such as pills,

pellets, extrudates, cakes, etc. When formed into As-inch by A s-inch cylindrical pills, the alumina-of the present invention has an apparent bulk density less than about 0.60 gram/cc, a surface area .of about 200 square meters per gram, a pore volume of about 0.428 and a pore diameter of about 80 Angstrom units.

When utilized as the carrier material in the manufacture of hydrocarbon hydrodesulfurization catalysts, the.

calcined alumina particles may be combined with the metallic components in any suitable, desired manner, A particularly convenient method of incorporating the cata lytically active metallic components with the carrier material involves impregnating techniques utilizing water-solw ble compounds of the metals to be composited therewith.

Suitable water-soluble compounds include nickel nitrate.

hexahydrate, nickel chloride, chloroplatinic acid,, molybdic acid, chloropalladic acid, .dinitritod-iamino platinum, etc. The metallic components will generally be composited with the. calcined alumina in amount up to about 30.0 percent by Weight, calculated as the elements thereof. Lesser quantities of the platinum-group metals will be utilized, and will lie Within the range of from about 0.01

will be employed within the range. of from about 1.0

percent to about 30.0 percent by Weight; when. the

,Group VI-A metallic component is molybdenum, the con-.

centration thereof will be from about 6.0 percent to about ponents are employed in quantities less than that of the calcination treatment, in the presence ofair, at a temperature of from about 400 C. to about 800 C. The metallic components, after being combined with the alumina, and following the last-mentioned calcination procedure, may-thereafter be treated'in such a manner .as to be caused to exist within the composite in any desired state, either asthe elements, 'or as compounds thereof. Thus, the composite may be sulfided, as with hydrogensulfide, whereby the metals exist as sulfides; the composite may be hydrogen-treated such that the metals exist in their most reduced form. In any event, the state of the metal 'lic components,"within the final composite, is not considered to be a feature limiting the broad scopeand spirit of the appended'claims.

' The hydrodesulfurizationcatalyst, prepared by utilizing the alumina of the present invention, may be employed to great advantage in processes designed to effect the preparation of saturated hydrocarbon charge stocks substantially free from combined sulfur and nitrogen. Recent developments Within the. petroleum industry have indicated thatcatalytic reforming processes utilizing acatalyst consisting primarilyof'platinum and alumina, and particularlya composite which also contains combined halogen, are especially useful in the reforming of hydrocarbons and mixtures of hydrocarbons for the purpose of increasing the anti-knock characteristics thereof. Through the proper selection of operating. conditions, these platinum-containing catalysts may be utilized for a relatively extendedperiod oftime when processing hydrocarbon fractions comparatively free from various contaminants. .Howeverg'when efiiecting these reactions while processing charge stocks containing excessive concentrations of contaminants, selective poisoning of the platinumcontaining catalyst results, accompanied by a significant decline in the activity and stability thereof.

Hydrodesulfurization catalysts are very effective in purifying hydrocarbon charge stocks in a manner whereby metalliccontaminants are removed, combined sulfur and nitrogen are converted to hydrogen'sulfide and ammonia, and olefinic hydrocarbons are saturatedto form parafiins and naphthenes. It becomes difficultto effect a success ful reforming process on an unsaturated charge stock 'containing large quantities of sulfurous and nitrogenous compounds; the unsaturated compounds exhibit the tendency to polymerize, forming acar-bonaceous material which becomes deposited upon the platinum-containing catalyst.

The sulfur and nitrogen compounds are caused to form hydrogen sulfide and ammonia, both of which exhibit adverse effects toward the'reforming catalyst. v

The following examples are given for the purpose of 1 illustrating the process of the present'invention, and in- 'not consideredto be outside the broad scope of the present invention. 7 I

In these examples, reference is made to a standard relative activity test method. The relative activity of a particular catalyst is defined as the ratio of the space velocity required to result in a given product improvement, while employing the test catalyst, to the space velocity required to yield the same degree of product improvement While employing a standard catalyst, which relative activity is expressed as a percentage. The catalyst employed as the standard relative catalyst was an alumina-cobalt-molybdenum composite consisting of about 2.2 percent by weight of cobalt and about 5.9 percent by weight of molybdenum, this catalyst being typical of the hydrodesulfurization catalysts currently manufactured. The product quality improvement was measured in terms of the residual basic nitrogen content of the liquid product: since the removal of nitrogenous compounds is that function of the catalyst most difiicult to achieve, the relative activity of the catalytic composite is more logically based thereon, rather than on an improvement in either the sulfur concentration or the quantity of olefinic hydrocarbons remaining in the hydrocarbon charge. The relative activity :test method consists essentially of processing a thermally-cracked California naphtha; this charge stock is characterized by an API gravity of 433 at 60 R, an initial volumetric distillation point of 290 F., a 50% distillation point .of 320 F., and an end boiling point of 392 F. The thermally-cracked naphtha contains 1.46 percent by weight of sulfur, 240 ppm. of basic nitrogen, and has a bromine number of 61, the latter indicating that the naphtha contains a significant quantity of olefinic hydrocarbons. The charge stock is passed into a reaction zone fabricated from l-inch, schedule 80, type 316 stainless steel, equipped with a thermocouple Well, to which perforated bafile plates are fastened to serve as the vaporization, preheating and mixing zone for hydrogen and the liquid hydrocarbon charge. The reactor contains a single catalyst bed of about 50 cubic centimeters, and is maintained under an imposed hydrogen pressure of about 800 pounds per square inch, hydrogen being recycled therethrough at a rate of about 3000 standard cubic feet per barrel of liquid charge; the inlet temperature to the catalyst in each instance is 700 F. Three distinct test procedures are effected at various liquid hourly space velocities within the range of about 2.0 to about 10.0. The liquid product effluent, upon which the product inspections are made, is collected over a period of operation of about four to about seven hours. The basic nitrogen concentration in each of the three liquid products are plotted on a logarithmic scale against the reciprocals of the three space velocities employed. From the resulting curve, drawn through the three points, a determination is made of the reciprocal of the space velocity required to yield a liquid product having a residual basic nitrogen content of two ppm. The relative activity of the test catalyst is derived from the ratio of the reciprocal space velocity to yield two parts per million basic nitrogen, in regard to the standard catalyst, and compared to that of the catalyst being tested. The ratio is multiplied by a factor of 100, and a relative activity factor greater than 100 indicates a test catalyst having a greater activity than the standard catalyst; obviously, a catalyst having a relative activity less than 100 is less active than the primary standard catalyst.

Example 1 The catalyst employed in this example was prepared by precipitating basic aluminum sulfate from a solution of aluminum sulfate by simultaneously commingling the latter with ammonium hydroxide at a controlled pH of about 6.0. Following an initial filtration step, the resulting filter cake was intimately commingled with a hot (178 F.) aqueous solution of 28.0 percent by weight of ammonium hydroxide in an amount to raise the pH of the resulting slurry to a level of about 8.0. The resulting slurry was again filtered, and again commingled with ammonium hydroxide to raise the pH to a level of 8.0;

this procedure was effected a total of five times, the final filter cake being dried at a temperature of about C., and thereafter calcined, in an atmosphere of air, at a temperature of about 500 C. The calcined alumina was formed into Aninch by Az-inch cylindrical pills, a 50- gram portion of the pills being impregnated with nickel and molybdenum. The impregnating solution consisted of 34.2 grams of molybdi'c acid (85.0 percent M00 21.0 'ml. of water and 42.0 ml. of a 28.0 percent by weight solution of ammonium hydroxide. This molybdenumcontaining solution was then commingled with a solution of 16.8 grams of nickel nitrate hexahydrate, 13.7 grams of nickel chloride hexahydrate, and about 50 m1. of ammonium hydroxide. Sutficient ammonium hydroxide was then added to the mixture to increase the total volume thereof to about m1. Following the impregnation, with the foregoing solution, the 50 grams of alumina were dried and calcined for a period of one hour at a temperature of 1100 F. The final catalyst contained 8.6 percent by weight of nickel oxide and 29.1 percent by weight of molybdenum oxide, computed on the basis of the weight of alumina. When subjected to the standard relative activity test procedure, hereinbefore described, this catalyst indicated a relative activity of 135.

Example II The catalyst of the present example was prepared by precipitating basic aluminum sulfate from 4232 ml. of an aluminum sulfate solution, having a specific gravity of about 1.28, using 1042 ml. of 28 per-cent by weight solution of ammonium hydroxide. The solutions of aluminum sulfate and ammonium hydroxide were added continuously and simultaneously to a large beaker at such rates as to maintain the pH of the resulting basic aluminum sulfate slurry at about 6.0. The initial filter cake was re-slurried with 45 ml. of concentrated hydrochloric acid in an additional 250 ml. of Water at a pH of about 7.0. This quantity of hydrochloric acid was suflicien-t to result in a formula weight ratio of alumina-equivalent to chloride ion of about 8.0. The slurry was again filtered, and subsequently washed wit-h hot (178 F.) ammonium hydroxide, which procedure was repeated a total of five times. The final alumina filter cake was dried at a temperature of about 150 C. and thereafter calcined, at a temperature of about 500 C., in an atmosphere of air. 40 grams of As-inch by Al-ll'lCh alumina pills, prepared from the foregoing calcined alumina, were impregnated with an impregnating solution containing 9.4 grams of molybdic acid in 9.0 ml. of water, 12 ml. of a 28 percent by weight solution of ammonium hydroxide, 4.55 grams of nickel nitrate hexahydrate and 4.0 grams of nickel chloride hexahydrate in sumcient ammonium hydroxide to bring the total volume of the mixture to 74 mrllrmeters. Following the impregnation, the composite was dried at a temperature of 150 C. and oxidized, in an atmosphere of air, at a temperature of 1100 F. Based upon the weight of the alumina carrier material, the catalyst contained 3.0 percent by weight of nickel oxide and 10.0 percent by weight of molybdenum oxide. When subjected to the standard relativity test procedure hereinalgove described, this catalyst indicated a relative activity 0 162.

The hydrodesulfurization catalyst, utilizing the alumina prepared in accordance with the method of the present invention (Example II), indicated a relative activity 27 units greater than that indicated by the catalyst prepared in accordance with Example I, the latter not being hydrolyzed in the presence of a chlorine-containing compound. It is significant that the catalyst of Example I contained approximately three times the concentration of catalytically active metallic components than the catalyst prepared with the alumina of the present invention. Of further significance is the fact that the catalyst of Example I, when analyzed for carbon deposition resulting from the standard relative activity test, indicated 1.95 percent by Weight of carbon; the catalyst of Example .11 indicated a lesser carbon concentration of 1.70 percent by weight.

The foregoing examples clearly indicate the method of the present invention in preparing alumina from aluminum sulfate, which alumina is advantageously employed in the manufacture of hydrocarbon hydrodesulfurization taining compound inan amount to form a slurry having 1 a formula weight ratio of alumina-equivalent to chloride said molybdenum is present in anamountof from about 6.0 percent to about 30.0 percent by weight of the alu mina, and said iron-group metallic component is present ion within the range of from about 3:1 to about 50:1, 7

'Washing the resulting hydrolyzed precipitate until the Washed precipitate contains less than about 2-0 percent by weight of sulfate, drying and calcining to produce alumina, combining at least one metallic component: selected from the group consisting of the metals of 1 Groups VI-A and VIII of the Periodic Tablewith the calcined alumina and thereafter drying and calcining the resulting composite.

2. The method of claim 1 further characterized in that said catalyst comprises molybdenum and a metallic component from the iron-group metals.

3. T he catalyst of claim 2 further characterized in that in an amount of from about 1.0 percent to about6.0 percent by weight of the alumin'a, said metallic components calculated as the elements. I 1 p 4. A method of. preparing a hydrodesulfurization catalyst' which comprises precipitating basic aluminum sulfate from asolution-of aluminum sulfate, hydrolyzing the resulting precipitate with hydrochloric acid in an amount to form a slurry having a formula weight ratio of alumina-equivalent to chloride ion within the range of 'from about 5:1 to about 15:.1, maintaining the resulting slurry at apH less than about 7 .0, washing the resulting h droly ed precipitate until the. washed precipitate contains less than about,'2.0 percent'by weight of sulfate, drying the washed precipitate and calcining the same at an elevated temperature, thereaftercombining with the calcined alumina, from about 6.0 percentfto about.30.0 percent by Weight of molybdenum and from about 1-0 percent to about 6.0 percent by weight of. nickel, calculated as the elements and based on the weight of thealurnina.

References Cited by the Examiner UNITED STATES PATENTS 2,867,581 1/59 Nahin 252-470 X y 2,914,488 11/59 Gllbent 252-463 X 3,027,232 3/62. Michalko 252 463 X 3,066,012 11/62 Wilson et al 252463 X MAURICE A, BRINDISLPrimary Examiner-l 

1. A METHOD OF PREPARING A HYDRODESULFURIZATION CATALYST WHICH COMPRISES INITIALLY PRECIPITATING BASIC ALUMINUM SULFATE FROM A SOLUTION OF ALUMINUM SULFATE, HYDROLYZING THE PRECIPITATE, WHILE MAINTAINING THE RESULTING SLURRY AT A PH LESS THAN ABOUT 7.0, WITH A CHLORINE-CONTAINING COMPOUND IN AN AMOUNT TO FORM A SLURRY HAVING A FORMULA WEIGHT RATIO OF ALUMINA-EQUIVALENT TO CHLORIDE ION WITHIN THE RANGE OF FROM ABOUT 3:1 TO ABOUT 50:1, WASHING THE RESULTING HYDROLYZED PRECIPITATE UNTIL THE WASHED PREPITATE CONTAINS LESS THAN ABOUT 2.0 PERCENT BY WEIGHT OF SULFATE, DRYING AND CALCINING TO PRODUCE ALUMINA, COMBINING AT LEAST ONE METALLIC COMPONENT SELECTED FROM THE GROUP CONSISTING OF THE METALS OF GROUPS VI-A AND VIII OF THE PERIODIC TABLE WITH THE CALCINED ALUMINA AND THEREAFTER DRYING AND CALCING THE RESULTING COMPOSITE. 